//========================================================//
// Cryptography md5                                       //
// Author: Kozlov Dmitry aka LandFox kozlov@ccfit.nsu.ru  //
// NSU FIT September - October 2004                       //
//========================================================//


#include <string.h>
#include <stdio.h>

#include "md5.h"

typedef const uint32 cuint32;

uint32 inline S(uint32& x, const uint32& n) {
	return ((x << n) | ((x & 0xFFFFFFFF) >> (32 - n)));
}

void inline P(cuint32 * X, uint32& a, uint32& b, uint32& c, uint32& d, cuint32& k, cuint32& s,cuint32& t, int round) {
	switch(round) {
		case 0: a += d ^ (b & (c ^ d)); break;
		case 1: a += c ^ (d & (b ^ c)); break;
		case 2: a += b ^ c ^ d; break;
		case 3: a += c ^ (b | ~d); break;
	}
	a+= X[k] + t;
	a = S(a,s) + b;
}

void MD5_Init( MD5_CTX *ctx )
{
	ctx->total[0] = 0;
	ctx->total[1] = 0;

	ctx->state[0] = 0x67452301;
	ctx->state[1] = 0xEFCDAB89;
	ctx->state[2] = 0x98BADCFE;
	ctx->state[3] = 0x10325476;
}

inline void md5_process( MD5_CTX *ctx, const uint8 data[64] )
{
	uint32 X[16], A, B, C, D;

	memcpy(X,data,64);

	A = ctx->state[0];
	B = ctx->state[1];
	C = ctx->state[2];
	D = ctx->state[3];

	P(X, A, B, C, D,  0,  7, 0xD76AA478 ,0);
	P(X, D, A, B, C,  1, 12, 0xE8C7B756 ,0);
	P(X, C, D, A, B,  2, 17, 0x242070DB ,0);
	P(X, B, C, D, A,  3, 22, 0xC1BDCEEE ,0);
	P(X, A, B, C, D,  4,  7, 0xF57C0FAF ,0);
	P(X, D, A, B, C,  5, 12, 0x4787C62A ,0);
	P(X, C, D, A, B,  6, 17, 0xA8304613 ,0);
	P(X, B, C, D, A,  7, 22, 0xFD469501 ,0);
	P(X, A, B, C, D,  8,  7, 0x698098D8 ,0);
	P(X, D, A, B, C,  9, 12, 0x8B44F7AF ,0);
	P(X, C, D, A, B, 10, 17, 0xFFFF5BB1 ,0);
	P(X, B, C, D, A, 11, 22, 0x895CD7BE ,0);
	P(X, A, B, C, D, 12,  7, 0x6B901122 ,0);
	P(X, D, A, B, C, 13, 12, 0xFD987193 ,0);
	P(X, C, D, A, B, 14, 17, 0xA679438E ,0);
	P(X, B, C, D, A, 15, 22, 0x49B40821 ,0);

	P(X, A, B, C, D,  1,  5, 0xF61E2562 ,1);
	P(X, D, A, B, C,  6,  9, 0xC040B340 ,1);
	P(X, C, D, A, B, 11, 14, 0x265E5A51 ,1);
	P(X, B, C, D, A,  0, 20, 0xE9B6C7AA ,1);
	P(X, A, B, C, D,  5,  5, 0xD62F105D ,1);
	P(X, D, A, B, C, 10,  9, 0x02441453 ,1);
	P(X, C, D, A, B, 15, 14, 0xD8A1E681 ,1);
	P(X, B, C, D, A,  4, 20, 0xE7D3FBC8 ,1);
	P(X, A, B, C, D,  9,  5, 0x21E1CDE6 ,1);
	P(X, D, A, B, C, 14,  9, 0xC33707D6 ,1);
	P(X, C, D, A, B,  3, 14, 0xF4D50D87 ,1);
	P(X, B, C, D, A,  8, 20, 0x455A14ED ,1);
	P(X, A, B, C, D, 13,  5, 0xA9E3E905 ,1);
	P(X, D, A, B, C,  2,  9, 0xFCEFA3F8 ,1);
	P(X, C, D, A, B,  7, 14, 0x676F02D9 ,1);
	P(X, B, C, D, A, 12, 20, 0x8D2A4C8A ,1);

	P(X, A, B, C, D,  5,  4, 0xFFFA3942 ,2);
	P(X, D, A, B, C,  8, 11, 0x8771F681 ,2);
	P(X, C, D, A, B, 11, 16, 0x6D9D6122 ,2);
	P(X, B, C, D, A, 14, 23, 0xFDE5380C ,2);
	P(X, A, B, C, D,  1,  4, 0xA4BEEA44 ,2);
	P(X, D, A, B, C,  4, 11, 0x4BDECFA9 ,2);
	P(X, C, D, A, B,  7, 16, 0xF6BB4B60 ,2);
	P(X, B, C, D, A, 10, 23, 0xBEBFBC70 ,2);
	P(X, A, B, C, D, 13,  4, 0x289B7EC6 ,2);
	P(X, D, A, B, C,  0, 11, 0xEAA127FA ,2);
	P(X, C, D, A, B,  3, 16, 0xD4EF3085 ,2);
	P(X, B, C, D, A,  6, 23, 0x04881D05 ,2);
	P(X, A, B, C, D,  9,  4, 0xD9D4D039 ,2);
	P(X, D, A, B, C, 12, 11, 0xE6DB99E5 ,2);
	P(X, C, D, A, B, 15, 16, 0x1FA27CF8 ,2);
	P(X, B, C, D, A,  2, 23, 0xC4AC5665 ,2);

	P(X, A, B, C, D,  0,  6, 0xF4292244 ,3);
	P(X, D, A, B, C,  7, 10, 0x432AFF97 ,3);
	P(X, C, D, A, B, 14, 15, 0xAB9423A7 ,3);
	P(X, B, C, D, A,  5, 21, 0xFC93A039 ,3);
	P(X, A, B, C, D, 12,  6, 0x655B59C3 ,3);
	P(X, D, A, B, C,  3, 10, 0x8F0CCC92 ,3);
	P(X, C, D, A, B, 10, 15, 0xFFEFF47D ,3);
	P(X, B, C, D, A,  1, 21, 0x85845DD1 ,3);
	P(X, A, B, C, D,  8,  6, 0x6FA87E4F ,3);
	P(X, D, A, B, C, 15, 10, 0xFE2CE6E0 ,3);
	P(X, C, D, A, B,  6, 15, 0xA3014314 ,3);
	P(X, B, C, D, A, 13, 21, 0x4E0811A1 ,3);
	P(X, A, B, C, D,  4,  6, 0xF7537E82 ,3);
	P(X, D, A, B, C, 11, 10, 0xBD3AF235 ,3);
	P(X, C, D, A, B,  2, 15, 0x2AD7D2BB ,3);
	P(X, B, C, D, A,  9, 21, 0xEB86D391 ,3);

	ctx->state[0] += A;
	ctx->state[1] += B;
	ctx->state[2] += C;
	ctx->state[3] += D;
}

void MD5_Update( MD5_CTX *ctx, const uint8 *input, uint32 length )
{
	uint32 left, fill;

	if( ! length ) return;

	left = ctx->total[0] & 0x3F;
	fill = 64 - left;

	ctx->total[0] += length;
	ctx->total[0] &= 0xFFFFFFFF;

	if( ctx->total[0] < length )
		ctx->total[1]++;

	if( left && length >= fill )
	{
		memcpy( (void *) (ctx->buffer + left),
			(void *) input, fill );
		md5_process( ctx, ctx->buffer );
		length -= fill;
		input  += fill;
		left = 0;
	}

	while( length >= 64 )
	{
		md5_process( ctx, input );
		length -= 64;
		input  += 64;
	}

	if( length )
	{
		memcpy( (void *) (ctx->buffer + left),
			(void *) input, length );
	}
}

static uint8 md5_padding[64] =
{
	0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
		0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
};

void MD5_Final( uint8 digest[16], MD5_CTX *ctx)
{
	uint32 last, padn;
	uint32 high, low;
	uint8 msglen[8];

	high = ( ctx->total[0] >> 29 )
		| ( ctx->total[1] <<  3 );
	low  = ( ctx->total[0] <<  3 );

	*(uint32 *)msglen = low;
	*(uint32 *)(msglen + 4) = high;
	last = ctx->total[0] & 0x3F;
	padn = ( last < 56 ) ? ( 56 - last ) : ( 120 - last );

	MD5_Update( ctx, md5_padding, padn );
	MD5_Update( ctx, msglen, 8 );

	memcpy(digest,ctx->state,16);
}

